#include <bits/stdc++.h>
using namespace std;
const int N = 5005;
const int MOD = 1e9 + 7;
int n, k, dp[N][N];
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> k;
//dp[i][j] la so cach xep hop sao cho con lai i keo, da xep j hop
dp[n][0] = 1;
for (int i = n; i > 0; --i)
for (int j = 0; j <= k; ++j)
if (dp[i][j]){
//Tao 1 hop moi
if (j < k)
dp[i - 1][j + 1] = (dp[i - 1][j + 1] + dp[i][j]) % MOD;
//Xep 1 vien keo vao hop hien tai
if (j)
dp[i - 1][j] = (dp[i - 1][j] + (dp[i][j] * 1LL * i) % MOD) % MOD;
}
// for (int i = n; i >= 0; --i)
// for (int j = 0; j <= min(i, k); ++j) if (dp[i][j])
// cout << i << " " << j << "\t" << dp[i][j] << "\n";
cout << dp[0][k];
}
